Free-living inferential modeling of blood glucose level using only noninvasive inputs

The goal of this work is to present a causation modeling methodology with the ability to accurately infer blood glucose levels using a large set of highly correlated noninvasive input variables over an extended period of time. These models can provide insight to improve glucose monitoring, and glucose regulation through advanced model-based control technologies. The efficacy of this approach is demonstrated using real data from a type 2 diabetic (T2D) subject collected under free-living conditions over a period of 25 consecutive days. The model was identified and tested using eleven variables that included three food variables as well as several activity and stress variables. The model was trained using 20 days of data and validated using 5 days of data. This gave a fitted correlation coefficient of 0.70 and an average absolute error (AAE) (i.e., the average of the absolute values for the measured glucose concentration minus modeled glucose concentration) of 13.3 mg/dL for the validation data. This AAE result was significantly better than the subject’s personal glucose meter AAE of 15.3 mg/dL for replicated measurements.     

Image Enhancement of Conventional Transverse-Axial Tomograms

An image processing system for image enhancement of conventional transverse axial tomography (TAT) is described. Conventional TAT means a tomography system in which the X-ray source and X-ray film move in a circular arc about the long axis of the patient, which is a different technique from computerized tomography. In the image processing system described, the original X-ray tomograms are digitized, high-pass filtered, and displayed on a TV monitor. The results of processing several clinical tomograms are shown, and definite improvements in the observed information are noted. The basic technique should be equally applicable to other conventional tomography systems, e.g., linear tomography or hypocycloidal tomography.     

Theoretical and experimental SAR distributions for interstitialdipole antenna arrays used in hyperthermia

Theoretical predictions and experimental measurements of power deposition in muscle tissue phantoms are compared for various arrays of microwave dipole antennas used for hyperthermia cancer therapy. The antennas are linear coaxial dipoles which are inserted into small nylon catheters implanted in the tumor volume. The specific absorption rate (SAR) patterns for a 2-cm square array of four 915-MHz antennas are presented for both resonant and nonresonant dipoles. Arrays of dipoles with lengths much shorter than the resonant half-wavelength have a far more reactive input impedance and a much smaller absolute SAR magnitude in the array center than is seen for arrays of resonant dipoles, and the maximum SAR shifts from the array center to the antenna surfaces. The absolute length of the volume heated by the small-diameter antennas with the longer half-wavelength was longer than that of the larger-diameter antennas. SAR distributions for 4-cm square arrays of eight and nine antennas fed with equal amplitude and phase are also compared. It is shown that much of the array volume has a power deposition less than 25% of the maximum SAR and that the distribution is nonuniform for both the eight- and nine-antenna configurations     

Report of an IEEE Task Force?An IEEE Opinion on Research Needs for Biomedical Engineerng Systems

MORE than 200 years ago, our forefathers made note of man's inalienable rights to life, liberty, and the pursuit of happiness. To the engineering community (applied science in the service of man), these may be coincident with applications to medicine and biology (biomedical engineering), defense, and entertainment. Biomedical engineering research has the distinction, among these three missions, of not only contributing to the quality of human life through the industrial economy but also to life itself?the most fundamental concern of all people. It is through biomedical engineering research that we have been able to learn much concerning the functioning of living systems, and it is through such knowledge that we have been able to develop improved clinical diagnosis, monitoring, and treatment, including life-sustaining devices and aids to the handicapped. Each step represents an improvement in the quality of life, and each step forms the foundation upon which to gain new knowledge to improve upon earlier developments.     

Winner-Takes-All Associative Memory: A Hamming Distance Vector Quantizer

We present a design methodology for mapping neuralyinspired algorithms for vector quantization, into VLSI hardware.We describe the building blocks used: memory cells, current conveyors,and translinear circuits. We use the basic building blocks todesign an associative processor for bit-pattern classification;a high-density memory based neuromorphic processor. Operatingin parallel, the single chip system determines the closest match,based on the Hamming distance, between an input bit pattern andmultiple stored bit templates; ties are broken arbitrarily. Energyefficient processing is achieved through a precision-on-demandarchitecture. Scalable storage and processing is achieved througha compact six transistor static RAM cell/ALU circuit. The singlechip system is programmable for template sets of up to 124 bitsper template and can store up to 116 templates (total storagecapacity of 14 Kbits). An additional 604 bits of auxiliary storageis used for pipelining and fault tolerance re-configuration capability.A fully functional 6.8 mm by 6.9 mmchip has been fabricated in a standard single–poly, double–metal2.0µmn–well CMOS process.     

Development of an automated turbidimetric immunoassay for quantification of bovine serum immunoglobulin G

OBJECTIVE: To develop an automated turbidimetric immunoassay (TIA) for measurement of bovine IgG. SAMPLE POPULATION: 24 bovine serum samples. PROCEDURE: IgG concentration was determined by use of the TIA, and results were compared with those of the radial immunodiffusion (RID) method. Variables were determined, using commercially available reagents and a clinical biochemical analyzer. For the TIA, polyclonal goat anti-bovine IgG (Fc specific) serum, bovine IgG calibrator serum, and polyethylene glycol reaction buffer were used. Sample concentrations were determined by the instrument, using the linear regression method of least squares. The accuracy of this assay was validated by referencing to a purified bovine IgG standard and by recovery of control standards. Parallelism was documented by assay linearity and serial sample dilution linearity. Interference resulting from hemolyzed samples was examined. RESULTS: The TIA method correlated positively (r = 0.9957) and significantly (P < 0.05) with the RID method, yielding a regression equation with slope of 0.78708 and y-intercept of 1.02102. Bias attributable to hemolysis was not observed. CONCLUSIONS: The TIA method is automated, accurate, and precise for bovine serum IgG quantification. CLINICAL RELEVANCE: This assay provides sample results in approximately 10 minutes and may be used as an alternative to the manual RID method.     

Comparison of power deposition by in-phase 433 MHz andphase-modulated 915 MHz interstitial antenna array hyperthermia systems

The interstitial microwave antenna array hyperthermia (IMAAH) system produces a pattern of specific absorption rate (SAR) that is nonuniform within a 2-cm square array when driven in phase at 915 MHz. It was found that phase modulation makes the time-averaged SAR pattern significantly more uniform in planes perpendicular to the antennas. To drive antennas in phase at 433 MHz similarly improves SAR uniformity when the antennas are of resonance length     

Laser scanning phase modulation microscope

We describe the concept and first implementation of an innovative new instrument for quantitative light microscopy. Currently, it provides selective imaging of optical path differences due to birefringence; with further development, it is also possible to selectively image several optical properties, including refractive path differences, optical rotation, and linear and circular dichroism, all with diffraction-limited resolution. An image consists of a 512×512 element array, with each pixel displaying one of 256 grey levels, linearly proportional to the specific optical property being observed. Additionally, conventional brightfield and polarized light microscopy are available, with the accompanying advantages of laser scanning and digital image processing. The microscope consists of three subsystems, representing three distinct technologies. The laser scanning subsystem moves a focused, microspot across the specimen; the output of a photodetector is an electric signal corresponding to a scanned image. The image display subsystem digitizes this signal and displays it as an image on a video monitor. When used in conjunction with a phase modulation feedback loop, the image formed is of the specimen's birefringent retardation or other selected optical property. The digitized images are also available for computer enhancement.     

Hybrid element method for unbounded electromagnetic problems in hyperthermia

Finite element and boundary element methods are described for predicting high-frequency electromagnetic heating of tissue as a cancer therapy. For the class of clinical problems of interest, the patient is electrically inhomogeneous and best discretized by finite elements, but the unbounded nature of practical source configurations calls for a boundary element approach. A hybrid is introduced which couples the two methods and is superior in algebraic requirements to either method alone. The formulation is three-dimensional and allows exact satisfaction of the electromagnetic jump conditions at interfaces separating distinct tissue types. Test cases show its validity for transverse magnetic and electric situations with known solutions. Examples of clinical applications are shown.     

Experience with a Multitransducer Ultrasound System for Localized Hyperthermia of Deep Tissues

A system employing six planar ultrasound transducers has been utilized for preclinical and pilot clinical studies with the aim of producing therapeutic heating preferentially at depth. The array consists of six 7 cm diameter PZT-4 disks mounted on a spherical shell section with a 26 cm radius of curvature. The crystals operate at different frequencies a few kilohertz above their fundamental frequencies of approximately 350 kHz for near-field peak suppression, and each has a few percent modulation to minimize standing wave effects. In water, the system can be focused to produce a high intensity region near the isocenter with a full width half maximum of approximately 1.5 cm in all directions. In attenuating tissue, the high intensity region is closer to the array of transducers by a few centimeters. For heating of realistic tumors at depth, small wedges are used to rotate the transducer axes a few degrees away from the radial direction, yielding a waist rather than a single point where the individual beam central axes come closest to each other. The waist is 3-6 cm in diameter, producing, ideally, ellipsoidal shaped temperature distributions centered deep in perfused tissue. Quantitative power deposition profile mapping, as well as qualitative studies using liquid crystal sheets, have been performed in water phantoms to characterize the system for different transducer orientations.